The invention herein resides in the art of dynamo-electric machines such as by-pass vacuum motors, wherein separate sources for working air and motor cooling air are provided. In such devices, one fan system is typically provided to move the working air while another fan system draws ambient air over the motor for cooling the motor""s windings. In particular, the invention relates to a motor cooling fan housing with a muffler which provides for radial inflow of cooling air so as to significantly reduce the amount of noise generated by the motor cooling fan.
By-pass vacuum motors are well-known in the art. By way of example only, wet vacuums are known wherein working air is entrained with water extracted from the surface. Since the working air is entrained with foreign matter, such as water and dirt, a separate fan is provided for purposes of generating airflow over the motor for cooling the same. If the motor is not cooled, the life of the motor is significantly reduced.
As with all vacuum motors, the operating noise levels associated therewith have always been a concern. Such noise is generally attributed to the fan tips passing by fixed elements in the fan and adjacent structure. Not only is the generated noise objectionable acoustically, it also represents wasted energy. Accordingly, it is desirable to reduce the amount of noise in vacuum motors.
Previously, it has been known to maintain the motor in a housing separate from the fan assembly for drawing in the working air. Maintained upon the motor housing is typically a motor cooling fan housing that receives a fan for drawing cooling air across the motor. One advancement in reducing cooling fan noise is exemplified in U.S. Pat. No. 4,684,835, which is incorporated herein by reference. In the aforementioned patent, the air is drawn axially in through the motor cooling fan housing by the motor cooling fan. The inventive concept in this patent is directed to the radially-directed and tapered configuration of the air inlets with respect to the cooling fan. Although this has been found to be an improvement over the art, the air is still drawn in axially and, as such, noise easily emanates from the cooling fan and surrounding housing.
Accordingly, there is a need in the art for a motor cooling fan housing in which the air inlets accommodate the air flow from outside the housing into the motor with reduced turbulence, perturbations, air vortex shedding, and resultant noise.
In light of the foregoing, it is thus an aspect of the present invention to provide a motor cooling fan housing having radial air inlets which are positioned above the motor cooling fan.
It is another aspect of the present invention to provide a motor cooling fan housing, as set forth above, wherein the cooling fan housing includes a muffler which is positioned in a plane above the cooling fan and which draws ambient air in radially to an area above the cooling fan and which then draws the gathered air in axially.
It is a further aspect of the present invention, as set forth above, wherein the muffler includes a plurality of vanes extending from a top plate to form radial air entry ports between the adjacent vanes.
It is yet another aspect of the present invention, as set forth above, to configure the vanes such that each has an outer radial portion which is concentrically aligned with the top plate""s outer periphery, and an inner radial portion extending in toward the top plate""s center from the outer radial portion.
It is yet another aspect of the present invention, as set forth above, to provide a muffler in either a unitary configuration such that it can be adapted to existing cooling fan motor housings, or to provide a Muffler that is integral with the cooling fan motor housing.
It is still another aspect of the present invention, as set forth above, to provide the muffler with a fan plate substantially parallel to the top plate and wherein a plurality of outer periphery walls connect the fan plate to the top plate and wherein an outer curvilinear wall extends inwardly from a corresponding outer periphery wall.
It is still a further aspect of the present invention, as set forth above, wherein each curvilinear wall extends inwardly from the corresponding outer periphery wall such that the radial air entry port is continuous with a flow opening centrally disposed between the fan plate and the top plate.
It is an additional aspect of the present invention, as set forth above, wherein the fan plate has a plurality of notches that are contiguous with the flow opening and wherein each notch is positioned between adjacent curvilinear walls.
The foregoing and other aspects of the present invention, which shall become apparent as the detailed description proceeds, are achieved by a bypass discharge motor assembly with improved noise reduction including a motor assembly having a rotatable shaft, a working air fan assembly rotated by the shaft, a cooling fan rotated by the shaft, and a cooling fan housing coupled to the motor assembly and partially enclosing the cooling fan, the cooling fan housing having at least one radial air entry port for radially receiving cooling air drawn into the housing by the cooling fan.
Other aspects of the present invention are attained by a muffler for motor assemblies that include a cooling fan comprising a top plate and a plurality of vanes extending from the top plate wherein adjacent vanes form a radial air entry port therebetween.
Still another object of the present invention is attained by a cooling fan housing for motor assemblies that include a cooling fan, including a sidewall and a muffler integrally extending from the sidewall, the muffler having at least one radial air entry port for receiving air drawn into the housing by the cooling fan.
These and other objects of the present invention, as well as the advantages thereof over existing prior art forms, which will become apparent from the description to follow, are accomplished by the improvements hereinafter described and claimed.